Currently, many small wastewater treatment systems use a septic tank, followed by a septic field for final purification and discharge. Increasingly, this method is becoming unacceptable because of the low level of treatment achieved, frequent failures and high cost of reconstruction, contamination of streams and groundwater, and the requirement for large land area to establish septic fields.
Japanese publication 2000-028675, German application DE 198 07 890 A1 and PCT publication No. WO 00/37369 describe wastewater treatment systems using membranes.
PCT Publication No. WO 00/21890 describes a cyclic aeration system.
Japanese publication JP 2002-066261 describes a device to catch fibrous foreign substances.